In the art processes have been described to maintain the antioxidant content of cocoa.
As an example, U.S. Pat. No. 6,660,332 discloses a cocoa bean processing technique that preserves the beneficial flavonoid compounds of cocoa beans in finished, cocoa bean-based foodstuffs.
This method avoids the significant losses of polyphenols that occur during conventional cocoa processing by removing a significant amount of said polyphenols prior to fermentation and/or roasting and then adding a portion of these polyphenols back.
In other methods that have been disclosed, antioxidant components/molecules are added at the end of the chocolate production process.
Typical preparation of “quality” chocolate consists of three stages: (1) mixing and possibly pre-grinding, (2) refining and most importantly (3) conching.
In the first step, the ingredients are mixed together in a kneader in order to get a paste. Generally, cocoa mass is mixed with sugar and possibly a small percentage of cocoa butter.
This paste may be subjected to a pre-grinding process in a 2-roll mill in order to obtain an overall fineness of about 150 μm. Sugar could also be pre-refined in a sugar mill.
In the second step, the actual refining step, the paste is passed on a multiple-roll equipment (generally with five rolls), where the fineness is reduced to an average of 10 to 30 μm. The product obtained is in powder form.
Most chocolate and certainly all “quality” products are then submitted to a third step, known already for a long time as “conching”.
During conching, the chocolate is subjected to a prolonged mechanical mixing combined with heating. This is carried out in special vessels known as “conches”.
Optional ingredients like cocoa butter and flavours are generally added at this stage.
Lecithin is hereby frequently added as an emulsifier to improve the rheological properties of chocolate, and thereby possibly enabling the amount of cocoa butter to be reduced. Other emulsifiers may also be used, like for example polyglycerol polyricinoleate and ammonium phosphatide.
During conching, the kneading action combined with high temperature causes evaporation of residual moisture and of some undesired volatile components such as acids generated during the fermentation of the cocoa beans.
The kneading action also leads to a better dispersion of sugar and cocoa particles in the fat phase formed by the cocoa butter released from the cocoa mass and possibly added.
The conching process results in the decrease of the viscosity and the yield value. At the end of the conching step, the chocolate has developed the right flavour and the desired rheological properties.
There are two types of conching operations, respectively known in the art as “dry” conching and “wet” conching (EP 0 489 515). In the following paragraphs: a description of a wet and dry conching as generally applied.
In “wet” (conventional) conching all the cocoa butter and other ingredients such as lecithin are added early in the process to maintain the fluidity of the mass which is then mechanically worked for a prolonged time, typically for about 20 or 30 hours or more, and at a relatively low temperature, typically at about 40° C. up to about 60° C.
The (conventional) “dry” conching process on the other hand is operated for a shorter time e.g. up to 20 hours but at a higher temperature mostly above 70° C. and usually about 90° C. for dark chocolate, and above 55° C. and usually around 80° for milk chocolate.
In this case, the extra cocoa butter and other ingredients are added towards the end of the conching period, e.g. about one hour before the end of the conching period. This last step (after the actual “dry conching”) is commonly known as “liquid conching”.
The aim of this treatment (“liquid conching”) is to homogenize and to obtain a liquid pumpable mass (EP 0 489 515; Beckett, S. T., 1994; Information given on the britanniafood website, Ziegleder, G., 2006).
Due to the technological evolution of the process equipment these two conching operations are nowadays generally realized in a shorter period of about 8 up to about 24 hours.
In the course of this three-step process (mixing & pre-grinding; refining; conching) it is of utmost importance to protect and preserve the development of antioxidants in the chocolate, as these play an important role in the defence mechanism of the body against free radicals.
Free radicals are molecules or atoms with one or more unpaired electrons. Due to this characteristic they are very reactive.
Free radicals play an important role in a lot of biochemical reactions, such as the intracellular killing of bacteria's and in certain cell signalling processes (Van Sant, G., 2004; information given on “free radicals” at the wikipedia website).
However, because of their reactivity, free radicals can damage protein-, fat-, and DNA-molecules in the (human) body.
They are thought to be the cause of some of the aging symptoms and believed to induce a lot of diseases like Parkinson, schizophrenia and Alzheimer diseases (“free radicals”, wikipedia website).
Free radicals are further involved in some of the main dead causes in the western world like some cancers types, coronary heart disease and cardiovascular diseases in general.
The body has a number of mechanisms to minimize these radical damages.
One of these defence mechanisms occurs through antioxidants. Antioxidants react with free radicals and by so doing make them harmless.
The best known antioxidants are the vitamins C, E, carotenoids and the polyphenols (Van Sant, G., 2004).
Polyphenols are a complex group of molecules which can be naturally found in the plant world. More than 8000 polyphenolic structures are known.
Polyphenols can be divided into different classes based upon their chemical structure: flavonoids, phenolic acids, stilbenes and lignans (Roura, E. et al., 2005).
Cocoa, the main ingredient of dark chocolate is rich in polyphenols, particularly in flavan-3-ols such as epicathechins, cathechins and procyanidins (Mursu, J. et al., 2004).
The primary family of flavanoids contributing to the antioxidant activity of chocolates is the procyanidins (Counet, C. & Collin, S., 2003). Their basic unit is a three-ring molecular structure (U.S. Pat. No. 6,660,332).
Procyanidins can be present as oligomers (2 to up to 10 flavan-3-ol units) or in the form of polymers with a higher degree of polymerization, the so called tannins.
The antioxidant activity of cocoa polyphenols is even higher than that of the more well-known antioxidant products like tea or wine (Lee, K. W. et al., 2003).
In 1999, the USDA (United State Department of Agriculture) has put plain chocolate on top of the list of antioxidant food (USDA, 1999).
The antioxidant capacity of cocoa products is further strengthened by the presence of melanoidins (Counet, C. & Collin, S., 2003).
Melanoidins are polyfunctional macromolecules formed by Maillard reactions. These brown nitrogen containing polymers with a molecular weight between 1,000 and 100,000 Da may also have phenolic units included in their structure.
Lately, more and more evidence has been found for the health benefits of eating dark chocolate.
Dark chocolate or cocoa consumption is supposed to favourably affect cardiovascular disease risk by slowing down LDL oxidation (Mursu, J. et al., 2004; Wan, Y. et al., 2001; Kondo, K. et al., 1996; Waterhouse, A. L. et al., 1996), increasing serum total antioxidant activity and HDL-cholesterol concentrations, and not adversely affecting prostaglandins (Wan, Y. et al., 2001).
The antioxidant activity of cocoa products is also beneficial as a defence against reactive oxygen species which are involved in immune response (Sanbongi, C. et al., 1997), and it is associated with improvement in endothelial and platelet function (Engler, M. B. et al., 2004; Hemann, F. et al., 2006) and with lowered blood pressure (Grassi, D. et al, 2005; Buijsse, B. et al., 2006).
Chocolate is considered as a widely consumed food. It is therefore highly desirable to develop processes that will provide chocolate contributing to general health improvement.